Ferromagnetic Coupling between Semiquinone Type Tridentate Radical Ligands Mediated by Metal Ions

Bruni, Silvia; Caneschi, Andrea; Cariati, F.; Delfs, Chris; Dei, Andrea; Gatteschi, Dante

doi:10.1021/ja00083a026

Cited by 135 publications

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“…Diamagnetic corrections estimated from the Pascal contents were applied to all data for determination of the molar paramagnetic susceptibilities of the compounds. NMR spectra were recorded by using a Bruker AV400 spectrometer equipped with a 5 mm triple resonance inverse probe with a dedicated 31 P channel operating at 500.33 MHz for 1 H equipped with a BVT3000 variable-temperature unit. TMS was used as an internal reference.…”

Section: Methodsmentioning

confidence: 99%

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Coexistence of Two Thermally Induced Intramolecular Electron Transfer Processes in a Series of Metal Complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)₂] (M=Co, Fe, and Ni) bearing Non‐Innocent Catechol‐Based Ligands: A Combined Experimental and Theoretical Study

Evangelio

Bonnet

Cabañas³

et al. 2010

Chemistry A European J

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The different thermally induced intermolecular electron transfer (IET) processes that can take place in the series of complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)2], for which M=Co (2), Fe (3) and Ni(4), and Cat‐N‐BQ and Cat‐N‐SQ denote the mononegative (Cat‐N‐BQ−) or dinegative (Cat‐N‐SQ2−) radical forms of the tridentate Schiff‐base ligand 3,5‐di‐tert‐butyl‐1,2‐quinone‐1‐(2‐hydroxy‐3,5‐di‐tert‐butylphenyl)imine, have been studied by variable‐temperature UV/Vis and NMR spectroscopies. Depending on the metal ion, rather different behaviors are observed. Complex 2 has been found to be one of the few examples so far reported to exhibit the coexistence of two thermally induced electron transfer processes, ligand‐to‐metal (IETLM) and ligand‐to‐ligand (IETLL). IETLL was only found to take place in complex 3, and no IET was observed for complex 4. Such experimental studies have been combined with ab initio wavefunction‐based CASSCF/CASPT2 calculations. Such a strategy allows one to solicit selectively the speculated orbitals and to access the ground states and excited‐spin states, as well as charge‐transfer states giving additional information on the different IET processes.

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Section: Methodsmentioning

confidence: 99%

“…Fortunately, resonance Raman (rR) studies of complexes 2 and 3 have already been reported in the literature. [31] The room-temperature (rR) spectrum of such complexes contains the vibrations of both electronic forms of the ligand, signifying that the ligands are not equivalent. Therefore, by comparing these results with those obtained for the slower probe .…”

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confidence: 99%

Coexistence of Two Thermally Induced Intramolecular Electron Transfer Processes in a Series of Metal Complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)₂] (M=Co, Fe, and Ni) bearing Non‐Innocent Catechol‐Based Ligands: A Combined Experimental and Theoretical Study

Evangelio

Bonnet

Cabañas³

et al. 2010

Chemistry A European J

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“…A striking example can be found in ligands derived from o-benzoquinones, that can bind metals as radical semiquinonates (SQ •− ) or as catecholates (Cat 2− ), depending also on the metal. Thus, the dianion from bis(2-hydroxy-3,5-di-tert-butylphenyl)amine with V(IV) is a catecholate and a semiquinonate contemporarily [127]. V(Cat-N-SQ) showed a quite complicated redox pattern.…”

Section: Non-oxido Vanadium(iv) Speciesmentioning

confidence: 99%

A journey into the electrochemistry of vanadium compounds

Galloni

Conte

2015

Coordination Chemistry Reviews

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“…Scandium and titanium ions are omitted, since very few results concerning them have been reported. 17,18 8.2 General properties of phenoxyl radicals 8…”

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Metal Coordinated Phenoxyl Radicals

Thomas

2010

Stable Radicals

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The term "phenoxyl" radical was first introduced in 1914 by Pummerer 1 to designate species involved in the oxidation of naphthols and phenanthroles. It was not until the 1960s that the existence of phenoxyls was demonstrated by Electron Paramagnetic Resonance (EPR). The term "stable" is commonly used to designate radicals such as nitroxides, trityls, and so on. Although the term "stable" had been associated with some phenoxyl radicals in 1967, 2 it must be realized that phenoxyl radicals exhibiting stabilities comparable to those of nitroxides were rather rare at this time. During the 1970s, Reichard et al . 3 demonstrated that radicals related to phenoxyls could also arise from mono-electronic oxidation of the phenolic side chain of tyrosines in some proteins, and thus could be involved in biological processes. The new term "tyrosyl" was then introduced to designate these residues, and many other biological systems involving such radicals have been described. 4,5 One of the more important recent advances in tyrosyl radical history was achieved in the 1990s with the characterization of the galactose oxidase (GO) active site. 6 -8 For the first time it was demonstrated that tyrosyls could exist coordinated to a metal ion. To better understand this association, chemists have subsequently developed many complexes involving coordinated phenoxyl radicals. 9 -13 Elucidation of the properties of coordination compounds involving redox active ligands, especially those involving sterically hindered phenolates, is one of the most recent and fascinating topics of interest in bioinorganic chemistry. The challenge in this kind of chemistry is the right description of the electronic structure of the M n+ -OPh entity (where OPh represents a phenolate group) once it has been oxidized by one electron. In principle, either the M (n+1)+ -OPh, that is the oxidation is metal based, or the M n+ -• OPh form, that is the oxidation is ligand based, could be obtained. The right description is thus not obvious and, as will be shown below, it strongly depends on the nature of the metal ion, the denticity of the ligand, the substituents of the phenolate precursor and even the temperature. Coordination is also found to improve the radical stability, and exerts an extraordinary control on their magnetic properties and reactivity (regio-and stereoselective oxidations are promoted by a radical). Stable Radicals: Fundamentals and Applied Aspects of Odd-Electron CompoundsEdited by Robin G. Hicks

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Ferromagnetic Coupling between Semiquinone Type Tridentate Radical Ligands Mediated by Metal Ions

Cited by 135 publications

References 0 publications

Coexistence of Two Thermally Induced Intramolecular Electron Transfer Processes in a Series of Metal Complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)₂] (M=Co, Fe, and Ni) bearing Non‐Innocent Catechol‐Based Ligands: A Combined Experimental and Theoretical Study

Coexistence of Two Thermally Induced Intramolecular Electron Transfer Processes in a Series of Metal Complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)₂] (M=Co, Fe, and Ni) bearing Non‐Innocent Catechol‐Based Ligands: A Combined Experimental and Theoretical Study

A journey into the electrochemistry of vanadium compounds

Metal Coordinated Phenoxyl Radicals

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Ferromagnetic Coupling between Semiquinone Type Tridentate Radical Ligands Mediated by Metal Ions

Cited by 135 publications

References 0 publications

Coexistence of Two Thermally Induced Intramolecular Electron Transfer Processes in a Series of Metal Complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)2] (M=Co, Fe, and Ni) bearing Non‐Innocent Catechol‐Based Ligands: A Combined Experimental and Theoretical Study

Coexistence of Two Thermally Induced Intramolecular Electron Transfer Processes in a Series of Metal Complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)2] (M=Co, Fe, and Ni) bearing Non‐Innocent Catechol‐Based Ligands: A Combined Experimental and Theoretical Study

A journey into the electrochemistry of vanadium compounds

Metal Coordinated Phenoxyl Radicals

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Coexistence of Two Thermally Induced Intramolecular Electron Transfer Processes in a Series of Metal Complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)₂] (M=Co, Fe, and Ni) bearing Non‐Innocent Catechol‐Based Ligands: A Combined Experimental and Theoretical Study

Coexistence of Two Thermally Induced Intramolecular Electron Transfer Processes in a Series of Metal Complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)₂] (M=Co, Fe, and Ni) bearing Non‐Innocent Catechol‐Based Ligands: A Combined Experimental and Theoretical Study